1
|
Macková K, Zahradníková A, Hoťka M, Hoffmannová B, Zahradník I, Zahradníková A. Calcium release-dependent inactivation precedes formation of the tubular system in developing rat cardiac myocytes. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2017; 46:691-703. [PMID: 28913625 DOI: 10.1007/s00249-017-1249-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 06/21/2017] [Accepted: 08/17/2017] [Indexed: 01/06/2023]
Abstract
Developing cardiac myocytes undergo substantial structural and functional changes transforming the mechanism of excitation-contraction coupling from the embryonic form, based on calcium influx through sarcolemmal DHPR calcium channels, to the adult form, relying on local calcium release through RYR calcium channels of sarcoplasmic reticulum stimulated by calcium influx. We characterized day-by-day the postnatal development of the structure of sarcolemma, using techniques of confocal fluorescence microscopy, and the development of the calcium current, measured by the whole-cell patch-clamp in isolated rat ventricular myocytes. We characterized the appearance and expansion of the t-tubule system and compared it with the appearance and progress of the calcium current inactivation induced by the release of calcium ions from sarcoplasmic reticulum as structural and functional measures of direct DHPR-RYR interaction. The release-dependent inactivation of calcium current preceded the development of the t-tubular system by several days, indicating formation of the first DHPR-RYR couplons at the surface sarcolemma and their later spreading close to contractile myofibrils with the growing t-tubules. Large variability of both of the measured parameters among individual myocytes indicates uneven maturation of myocytes within the growing myocardium.
Collapse
Affiliation(s)
- Katarina Macková
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia
| | - Alexandra Zahradníková
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia
| | - Matej Hoťka
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia
| | - Barbora Hoffmannová
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia
| | - Ivan Zahradník
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia
| | - Alexandra Zahradníková
- Department of Muscle Cell Research, Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05, Bratislava, Slovakia.
| |
Collapse
|
2
|
Gerdes AM. How to improve the overall quality of cardiac morphometric data. Am J Physiol Heart Circ Physiol 2015; 309:H9-H14. [PMID: 25957219 DOI: 10.1152/ajpheart.00232.2015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 05/04/2015] [Indexed: 01/06/2023]
Abstract
By the mid-1990s, experts realized that drugs leading to improved ventricular remodeling were doing something remarkable in cardiac patients. The "age of cardiac remodeling" had begun. This created an experimental need for high-quality assessment of changes in cardiac tissue composition, including myocyte shape, myocardial fibrosis/collagen, and vascular remodeling. Many working in the field today have little or no training related to recognition of fixation artifacts or common errors associated with quantitative morphology. Unfortunately, such skills had become somewhat of a lost art during the ages of cardiac physiology in the mid-20th century and molecular biology, gaining prominence by the mid-1970s. Consequently, cardiac remodeling studies today are often seriously flawed to the point where data are not reproducible and subsequent researchers may be chasing the molecular basis of a nonexistent or erroneous phenotype. The current unacceptably high incidence of irreproducible data is a serious waste of time and resources as recently noted in comments by the National Institutes of Health director. The goal of this "how to" article is to share some lessons I have learned during nearly 40 years of assessing morphological changes in the heart. It is possible for any laboratory to routinely publish highly reproducible morphological data that stand the test of time and contribute to our fundamental knowledge of cardiac remodeling and the molecular mechanisms that drive it.
Collapse
Affiliation(s)
- A Martin Gerdes
- Department of Biomedical Sciences, New York Institute of Technology-College of Osteopathic Medicine, Old Westbury, New York
| |
Collapse
|
3
|
Wu Y, Wu EX. MR study of postnatal development of myocardial structure and left ventricular function. J Magn Reson Imaging 2009; 30:47-53. [DOI: 10.1002/jmri.21814] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
|
4
|
Velkoska E, Cole TJ, Dean RG, Burrell LM, Morris MJ. Early undernutrition leads to long-lasting reductions in body weight and adiposity whereas increased intake increases cardiac fibrosis in male rats. J Nutr 2008; 138:1622-7. [PMID: 18716160 DOI: 10.1093/jn/138.9.1622] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Previous studies suggest that both overfeeding and undernutrition during development increase the risk of obesity and hypertension in adulthood. In this study, we examined both short- (24 d) and long- (16 wk) term effects of early postnatal over- and underfeeding in rats on body weight, body composition, plasma hormones, adiposity markers, and hypothalamic neuropeptide Y content. Cardiovascular changes were also examined by measuring blood pressure and cardiac fibrosis. Rats raised in litters of 3, 12, or 18 pups per mother were used to model early onset overfeeding, control, and underfeeding, respectively. At 24 d of age, pups raised in small litters (SL) were 10% heavier than pups from normal litters, accompanied by increased organ mass and fat mass, elevated plasma leptin, corticosterone, and uncoupling protein-1 mRNA in brown adipose tissue. On the other hand, pups raised in large litters were 17% lighter with no significant changes in plasma leptin. Overfeeding during the first 3 wk of life led to increased plasma leptin concentration in adulthood, whereas underfed rats remained significantly lighter throughout the study, with no evidence of catch-up growth. Rats raised in SL were more susceptible to developing cardiac fibrosis with a 22% increase in collagen deposition compared with control rats at 16 wk of age (P < 0.05). This was independent of any changes in blood pressure. This study demonstrates that nutritional changes early in postnatal development can have long-lasting effects on body weight, adiposity, and some mediators involved in energy homeostasis and can also lead to structural changes in the heart in adulthood. This highlights the importance of identifying potential early life risk factors involved in the modulation of childhood nutrition.
Collapse
Affiliation(s)
- Elena Velkoska
- Department of Pharmacology, University of Melbourne, Parkville, 3010, Australia
| | | | | | | | | |
Collapse
|
5
|
Minami S, Onodera T, Okazaki F, Miyazaki H, Ohsawa S, Mochizuki S. Myocyte Morphological Characteristics Differ Between the Phases of Pulmonary Hypertension-Induced Ventricular Hypertrophy and Failure. Int Heart J 2006; 47:629-37. [PMID: 16960417 DOI: 10.1536/ihj.47.629] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Pulmonary hypertensive model rats were prepared by treating them with monochrotaline (MCT). Using these model rats, we examined myocyte remodeling in the right ventricle in response to increased right ventricular pressure. Male Sprague-Dawley rats were divided into 2 groups. Group M received MCT and group C received physiological saline. The 2 groups were examined at weeks 2, 5, and 7 after MCT or saline injection, respectively. At week 2, a significant difference in cell form was not observed in either group. At week 5, cell volume and myocyte cross-sectional area (CSA) of the right ventricle in group M were significantly greater than those in group C. At week 7, cell volume, CSA, and cell length of the right ventricle in group M were all significantly greater than those in group C. These results suggest that pulmonary hypertension causes hypertrophy, accompanying the enlargement of CSA in the right ventricle, and that cells lengthen in the phase of right ventricular failure. These results are similar to the changes observed in left ventricular myocytes due to overload pressure. Both right and left ventricular myocytes may share a common mechanism for myocyte remodeling as an adaptive and maladaptive response to increased ventricular pressure.
Collapse
Affiliation(s)
- Shunrou Minami
- Division of Cardiology, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | | | | | | | | | | |
Collapse
|
6
|
Corstius HB, Zimanyi MA, Maka N, Herath T, Thomas W, van der Laarse A, Wreford NG, Black MJ. Effect of intrauterine growth restriction on the number of cardiomyocytes in rat hearts. Pediatr Res 2005; 57:796-800. [PMID: 15774830 DOI: 10.1203/01.pdr.0000157726.65492.cd] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Epidemiologic studies have linked intrauterine growth restriction (IUGR) with an increased incidence of cardiovascular disease later in life; reduced cardiomyocyte number in IUGR hearts may underlie such prenatal programming. Our aim was to examine the effect of IUGR, as a result of maternal protein restriction, on the number of cardiomyocytes in the rat heart at birth. Rats were fed either a low-protein diet (LPD) or a normal-protein diet (NPD) during pregnancy. At birth, the offspring were killed and the hearts were immersion-fixed. The number of cardiomyocyte nuclei in the hearts were stereologically determined using an optical disector-fractionator approach. In some litters, cardiomyocytes were enzymatically isolated from freshly excised hearts and the proportion of binucleated cells was determined. Taking into account the number of binucleated cells, the nuclear counts were adjusted to estimate total cardiomyocyte number. Birth weight and heart weight were significantly reduced in the LPD offspring. This was accompanied by a significant reduction in the number of cardiomyocytes per heart in the LPD offspring compared with the NPD offspring (1.18 +/- 0.05 x 10(7) and 1.41 +/- 0.06 x 10(7), respectively; p = 0.001). The number of binucleated cardiomyocytes was low (approximately 3%) and equal in both groups. In conclusion, IUGR as a result of maternal protein restriction leads to a reduction in the number of cardiomyocytes per heart. As cardiomyocyte proliferation is rare after birth, it is plausible that this reduction in cardiomyocytes may lead to compromised cardiac function later in life.
Collapse
Affiliation(s)
- Hugo Brandt Corstius
- Department of Cardiology, Leiden University Medical Centre, Leiden 2300 RC, The Netherlands
| | | | | | | | | | | | | | | |
Collapse
|
7
|
Onodera T, Okazaki F, Miyazaki H, Minami S, Ito T, Seki S, Taniguchi M, Taniguchi I, Mochizuki S. Perindopril reverses myocyte remodeling in the hypertensive heart. Hypertens Res 2002; 25:85-90. [PMID: 11924731 DOI: 10.1291/hypres.25.85] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Studies have shown that the renin-angiotensin system (RAS) plays an important role in cardiac remodeling induced by hypertension. However, the role of this system on myocyte remodeling remains unclear. In the present study, we have assessed the effect of perindopril, an angiotensin converting enzyme (ACE) inhibitor, in spontaneously hypertensive rats (SHRs) as a means to evaluate the role of RAS in myocyte remodeling. We also investigated the effect of beta blockade on myocyte remodeling. We used female SHRs at 12 weeks of age. They were divided into four experimental groups: a control group, group C; low dose perindopril group (0.3 mg/kg/day, p.o.), group PL; high dose perindopril group (3 mg/kg/day, p.o.), group PH; and bisoprolol group (60 mg/kg/day, p.o.), group B. We isolated myocytes from these rats after 4 weeks. LV myocyte volume and cross-sectional area decreased in groups PL and PH compared to group C. LV myocyte length decreased in group PH compared to group C. However, there was no morphological change in LV myocytes in group B compared to group C. In summary, ACE inhibitors reversed cardiac hypertrophy mainly by a reduction in LV myocyte volume; however, beta blockade did not reverse myocyte remodeling. These results suggest that RAS plays an important role in myocyte remodeling in the hypertensive heart.
Collapse
Affiliation(s)
- Tatsuyuki Onodera
- Department of Internal Medicine, The Jikei University School of Medicine, Tokyo, Japan.
| | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Abstract
In this review, we attempt to outline the age-dependent interactions of principal systems controlling the structure and function of the cardiovascular system in immature rats developing hypertension. We focus our attention on the cardiovascular effects of various pharmacological, nutritional, and behavioral interventions applied at different stages of ontogeny. Several distinct critical periods (developmental windows), in which particular stimuli affect the further development of the cardiovascular phenotype, are specified in the rat. It is evident that short-term transient treatment of genetically hypertensive rats with certain antihypertensive drugs in prepuberty and puberty (at the age of 4-10 wk) has long-term beneficial effects on further development of their cardiovascular apparatus. This juvenile critical period coincides with the period of high susceptibility to the hypertensive effects of increased salt intake. If the hypertensive process develops after this critical period (due to early antihypertensive treatment or late administration of certain hypertensive stimuli, e.g., high salt intake), blood pressure elevation, cardiovascular hypertrophy, connective tissue accumulation, and end-organ damage are considerably attenuated compared with rats developing hypertension during the juvenile critical period. As far as the role of various electrolytes in blood pressure modulation is concerned, prohypertensive effects of dietary Na+ and antihypertensive effects of dietary Ca2+ are enhanced in immature animals, whereas vascular protective and antihypertensive effects of dietary K+ are almost independent of age. At a given level of dietary electrolyte intake, the balance between dietary carbohydrate and fat intake can modify blood pressure even in rats with established hypertension, but dietary protein intake affects the blood pressure development in immature animals only. Dietary protein restriction during gestation, as well as altered mother-offspring interactions in the suckling period, might have important long-term hypertensive consequences. The critical periods (developmental windows) should be respected in the future pharmacological or gene therapy of human hypertension.
Collapse
Affiliation(s)
- J Zicha
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
| | | |
Collapse
|
9
|
Pelouch V, Kolár F, Milerová M, Ostádal B. Effect of the preweaning nutritional state on the cardiac protein profile and functional performance of the rat heart. Mol Cell Biochem 1997; 177:221-8. [PMID: 9450666 DOI: 10.1023/a:1006823608341] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The aim of the study was to find out whether the changes in nutritional status induced by different litter size during early postnatal development can influence quantitative and qualitative protein remodeling and contractile performance of the myocardium. Male Wistar rats born at the same day were pooled together at 2 days postbirth and assigned by random selection to dams in groups of 4, 8 or 16 rats/litter. The animals were investigated at the age of 4 and 16 weeks. The results revealed that the early postnatal nutritional modification altered weight parameters: whereas lower heart weight persisted in slow-growing rats until 16 weeks, higher body weight of fast-growing rats returned to the control level at the age of 16 weeks. Altered nutritional status influenced also protein remodeling of the myocardium: the concentration of all noncollagenous proteins (fractions of metabolic and contractile proteins) significantly increased in slow-growing rats, on the other hand, the concentration of collagenous proteins (pepsin-soluble and -insoluble fractions) was higher in fast-growing animals. The changes were, however, only transitional: three months after the end of the weaning period most protein changes returned to the control level. However, higher concentration of total blood lipids and triglycerides in fast-growing rats persisted until adulthood. Nutritional changes had, however, only minor effect on ventricular performance. No differences among groups were observed in basal values of the left ventricular pressure, while the maximum pressure attained after an acute ventricular loading and the contractile reserve were significantly decreased in slow-growing 4 week old rats. The functional consequence of altered nutritional status during weaning was only transitional, in agreement with the transient character of most structural and biochemical markers of myocardial remodeling.
Collapse
Affiliation(s)
- V Pelouch
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague
| | | | | | | |
Collapse
|
10
|
Gerdes AM. A reliable, efficient, and comprehensive approach to assess myocyte remodeling in cardiac hypertrophy and failure. J Card Fail 1997; 3:63-8. [PMID: 9110256 DOI: 10.1016/s1071-9164(97)90009-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Interest in ventricular remodeling has increased in recent years due to the development of new therapeutic agents which may produce beneficial changes in cardiac anatomy. Data collected with new techniques have provided a clear and consistent picture of myocyte remodeling in cardiac hypertrophy and failure. A maladaptive change in cardiac myocyte shape has been demonstrated in experimental animals with heart failure and in patients with congestive heart failure due to ischemic and idiopathic dilated cardiomyopathy. This article details an approach to collect comprehensive and reliable data on myocyte shape in an efficient manner using isolated myocytes. The methodology employs a Coulter Channelyzer (Model C256, Coulter Electronics, Inc., Hialeah, FL), a light microscope, and an image analysis system. Underlying problems associated with structural assessment of the heart are discussed and effective solutions are outlined.
Collapse
Affiliation(s)
- A M Gerdes
- Department of Anatomy and Structural Biology, University of South Dakota, Vermillion 57069, USA
| |
Collapse
|
11
|
Engelmann GL, Campbell SE, Rakusan K. Immediate postnatal rat heart development modified by abdominal aortic banding: analysis of gene expression. Mol Cell Biochem 1996; 163-164:47-56. [PMID: 8974039 DOI: 10.1007/bf00408640] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Proliferative growth of the ventricular myocyte (cardiomyocyte) is primarily limited to embryonic, fetal and very early neonatal periods of heart development. In contrast, cardiomyocyte maturation, as evidenced by cellular hypertrophy, is a long-term process that can occupy the bulk of the life-span of the mature organism. As the newborn myocyte undergoes a 'transition' from proliferative to hypertrophic growth, ventricular remodeling of the non-myocyte compartment is characterized by increased extracellular matrix (ECM) formation and coronary capillary angiogenesis. A role for ventricular-derived growth factors (GFs) in these inter-related processes are examined in an animal model of altered heart development produced by neonatal aortic banding. The suprarenal abdominal aorta of five day old rat pups were banded (B), sham operated (S), or untreated (C) and ventricular tissue (left ventricular free wall and septum) obtained at 7-, 14-, and 21-days post-intervention. Using Northern blot RNA hybridizations, expression of growth factors (GFs) and/or GF-receptors (GFR's) temporally associated with heart development were evaluated. Transcript levels for TGF-beta 1, IGF-II, and their associated cell surface receptors were increased in B animals. Concomitant changes in extracellular matrix (ECM) genes (as evaluated by Collagens Type I, III, and IV) were also increased in B animals. In addition, transcript levels for the vascular morphogenesis and remodeling-related protein SPARC (Secreted Protein, Acidic and Rich in Cysteine) was also elevated in the B animals. In several instances, S animals demonstrated changes in steady state transcript levels for genes which may influence myocyte maturation during the postnatal period. This suggests that normal autocrine/paracrine growth regulatory stimuli and responses can be modified (by surgical intervention and/or abdominal aortic banding) and these perturbations in gene expression may be related to previously documented changes in myocyte cell number, vascular composition, and ventricular architecture of the banded, neonatal heart. Future studies using this model will provide an opportunity to evaluate and possibly identify the stimuli and signal transduction machinery that regulate the final phases of myocyte proliferation, stimulate capillary formation and ECM deposition, and orchestrate the transition to hypertrophic growth during heart development.
Collapse
Affiliation(s)
- G L Engelmann
- Department of Medicine and Cell Biology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA
| | | | | |
Collapse
|
12
|
Abstract
BACKGROUND In the embryonic heart, the individual cardiac segments show different growth rates. For the analysis of changing form in relation with changing function, data on number and shape of cardiomyocytes are necessary. Such data will give insight into the process of hypertrophy and/or hyperplasia as they may take place in the myocardium in the embryonic period. METHODS We have measured the volumes of the nuclei and myocytes as well as the surface areas of the nuclear envelope and cellular membrane using stereological tools in rat embryos from 11 days postcoitum to 17 days postcoitum. From the data of the cellular volume of the myocytes and the myocardial volume of the individual segments, we have calculated the total number of myocytes during the developmental period. RESULTS It is shown that the sinus venosus, sinu-atrial junction, and atrium increase their cellular volume during development, whereas the other cardiac segments show no difference in cellular volume. Similarly, the surface area of the cell membrane of the sinus venosus and sinu-atrial junction had increased during development. The nuclear volume and the surface area of the nuclear envelope did not differ during the period studied. The total number of myocytes showed a conspicuously smaller increase in the atrio-ventricular canal and distal outlet segment than in the other segments. CONCLUSIONS The increase of the cellular volume in the segments sinus venosus and sinu-atrial junction seems to be due to a late differentiation process. In general, however, the increase of the myocardial volume in the individual cardiac segments is caused by hyperplasia of the cardiomyocytes in these segments and not by hypertrophy. The surface area of cells has a fixed relationship with cell volume, indicating that no important changes take place in the developmental period studied.
Collapse
Affiliation(s)
- M W Knaapen
- Department of Anatomy and Embryology, Leiden, Netherlands
| | | | | |
Collapse
|
13
|
|
14
|
Sarkisov DS, Arefyeva AM, Panova NW, Gvasava IG. Polyploidy in cardiac myocytes of normal and hypertrophic human hearts; range of values. Virchows Arch 1994; 424:429-35. [PMID: 8205355 DOI: 10.1007/bf00190566] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Two-wavelength scanning DNA cytophotometry was used for DNA and protein estimation in human ventricular myocytes. In many hypertrophic hearts weighing more than 500 g the DNA content assessed by ploidy of myocytes, was within the range of normal adult variation (4-10c, where c is the haploid DNA content). A correlation was found between the protein content of myocytes and the weight of the hypertrophic ventricle. In congenital heart disease, the excessive polyploidy (up to 15-20c) developed through the normal route of myocyte polyploidization in childhood. Excessive polyploidization was revealed only in overloaded hypertrophied ventricles. A correlation was identified between the ploidy level, the ventricular weight and age of the child. Excessive polyploidy was also detected in adults with congenital or acquired in childhood diseases. There was no correlation between the myocyte ploidy and age. We propose that childhood polyploidy excess persists in these adults. The ranges of polyploidy are compared with the recent data on genome: protein ratio in cardiac myocytes and the interrelationships allow us to discuss the significance of childhood heart polyploidy as a reserve utilised under pathological conditions in adults.
Collapse
|
15
|
Pelouch V, Dixon IM, Golfman L, Beamish RE, Dhalla NS. Role of extracellular matrix proteins in heart function. Mol Cell Biochem 1993; 129:101-20. [PMID: 8177233 DOI: 10.1007/bf00926359] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The cardiac interstitium is populated by nonmyocyte cell types including transcriptionally active cardiac fibroblasts and endothelial cells. Since these cells are the source of many components of the cardiac extracellular matrix, and because changes in cardiac extracellular matrix are suspected of contributing to the genesis of cardiovascular complications in disease states such as diabetes, hypertension, cardiac hypertrophy and congestive heart failure, interest in the mechanisms of activation of fibroblasts and endothelial cells has led to progress in understanding these processes. Recent work provides evidence for the role of the renin-angiotensin-aldosterone system in the pathogenesis of abnormal deposition of extracellular matrix in the cardiac interstitium during the development of inappropriate cardiac hypertrophy and failure. The cardiac extracellular matrix is also known to change in response to altered cardiac performance associated with post-natal aging, and in response to environmental stimuli including intermittent hypoxia and abnormal nutrition. It is becoming clear that the extracellular matrix mainly consists of molecules of collagen types I and III; they form fibrils and provide most of the connective material for typing together myocytes and other structures in the myocardium and thus is involved in the transmission of developed mechanical force. The data available in the literature support the view that the extracellular matrix is a dynamic entity and alterations in this structure result in the development of heart dysfunction.
Collapse
Affiliation(s)
- V Pelouch
- Division of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, Faculty of Medicine, University of Manitoba, Winnipeg, Canada
| | | | | | | | | |
Collapse
|
16
|
Liebman J, Thomas CW, Rudy Y. ECG body surface potential mapping many years after successful surgery for coarctation of the aorta. J Electrocardiol 1993; 26:25-41. [PMID: 8433054 DOI: 10.1016/0022-0736(93)90064-k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Patients with coarctation of the aorta (CoA) who previously underwent successful surgery are often diagnosed on standard electrocardiograms as having partial right bundle branch block. After surgery 24 patients with CoA had body surface potential mapping (BSPM) with the Case Western Reserve University 180 electrode system; of these 7 had additional aortic stenosis and none had ever had intracardiac communication. The average age at the initial surgery for CoA was 4.0 +/- 3.3 years and at the time of the BSPM it was 12.7 +/- 5.9 years. For the 17 patients with CoA without aortic stenosis the average age at the initial surgery was 5.0 +/- 3.4 years and at the time of the BSPM it was 14.2 +/- 6.0 years. In 11 of the 24 patients, a cardiac catheterization was performed, and each patient demonstrated normal pulmonary artery and right ventricular systolic pressure except for one child with 40 mmHg systolic. In the others all indications were that right ventricular pressure was normal. In 11 of the 24 patients, congestive heart failure had been present in infancy. All 24 cases had evidence for epicardial right ventricular breakthrough on the BSPM, a finding believed to indicate right ventricular activation from endocardium to epicardium via the normal Purkinje system. There were no findings on the BSPM suggesting that right bundle branch block was present. Right ventricular hypertrophy with or without terminal right conduction delay was present on the BSPM in 19 of the 24 patients (9 with additional left ventricular hypertrophy--left ventricular hypertrophy alone in 5). Right ventricular hypertrophy could be considered in 6 of 19 patients in the electrocardiogram, and in 11 of 19 in the vectorcardiogram. The mechanism for the persistent electrocardiographic right ventricular hypertrophy is postulated to involve right ventricular hyperplasia in utero or in early neonatal life, which never disappears.
Collapse
Affiliation(s)
- J Liebman
- Division of Pediatric Cardiology, Rainbow Babies and Children's Hospital, Cleveland, Ohio 44106
| | | | | |
Collapse
|
17
|
Brodsky VYa, Chernyaev AL, Vasilyeva IA. Variability of the cardiomyocyte ploidy in normal human hearts. VIRCHOWS ARCHIV. B, CELL PATHOLOGY INCLUDING MOLECULAR PATHOLOGY 1992; 61:289-94. [PMID: 1685821 DOI: 10.1007/bf02890430] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We have performed cytophotometry for DNA in isolated myocytes of the left ventricle from 16 men, aged 19-39 years, who died from various non-cardiac or pulmonary causes. The mean ploidy of myocytes varied from 3.2-3.9 c to 6.6-7.3 c in different layers of the anterior wall of the left ventricle (where c is the haploid DNA content measured by cytophotometry in Feulgen-stained preparations). There was no correlation between the layers. The percentage of binuclear cells varied from 25 to 86% and correlated in every layer with the mean ploidy value of the whole myocyte population. Approximate calculation of total ploidy revealed low values in the ventricles of some individuals, and high values in others. Averaging the values for all the hearts studied obscures this variation. Mean myocyte ploidy in different layers of the anterior wall was similar: in the external layer it was 5.1 +/- 0.3 c, in the middle layer 5.5 +/- 0.3 c and in the inner layer 4.8 +/- 0.4 c. The mean percentage of binuclear myocytes in these three layers was also similar, being 61 +/- 3%, 63 +/- 4% and 54 +/- 5%, respectively. Myocyte ploidy in tissue from the posterior wall of the left ventricle also varied, but was always higher than for the same layer of the anterior wall in the same ventricle. We propose that high or low myocyte ploidy, as well as different proportions of mono- and binucleate cells, can be a factor affecting the course and result of cardiac pathology in the absence of any changes of myocyte genome determined during early ontogenesis and representing a stable characteristic of the individual.
Collapse
Affiliation(s)
- Brodsky VYa
- Institute of Developmental Biology, USSR Academy of Sciences, Moscow
| | | | | |
Collapse
|
18
|
Di Donato RM, Fujii AM, Jonas RA, Castañeda AR. Age-dependent ventricular response to pressure overload. J Thorac Cardiovasc Surg 1992. [DOI: 10.1016/s0022-5223(19)34741-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
19
|
Hiraishi S, Agata Y, Nowatari M, Oguchi K, Misawa H, Hirota H, Fujino N, Horiguchi Y, Yashiro K, Nakae S. Incidence and natural course of trabecular ventricular septal defect: two-dimensional echocardiography and color Doppler flow imaging study. J Pediatr 1992; 120:409-15. [PMID: 1538287 DOI: 10.1016/s0022-3476(05)80906-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
This study was designed to determine the prevalence of trabecular ventricular septal defect (t-VSD) in neonates and to evaluate the effects of its location, morphologic features, and size on its natural course during infancy. One thousand twenty-eight term newborn infants were examined by color Doppler flow imaging with orthogonal ultrasonographic views. Ten girls and 11 boys (2.0%) were found to have t-VSD. The natural course of the defect was examined in 42 consecutive cases, consisting of this group of 21 neonates and another group of 21 neonates with t-VSD. The morphologic features of the defect within the trabecular septum were classified as one or two defects (36 cases) and as a mesh-like defect (six cases). Reduction in size began from the right ventricular side or from within the trabecular septum. Spontaneous closure occurred most commonly during the first 6 months of life and was observed in 32 cases (76%) by 12 months of age: the frequency of closure was not related to the morphologic features and the initial size of the defect, but apical defects tended to have higher persistent patency than did defects in other locations (p less than 0.05). We conclude that the frequency of t-VSD in neonates and the frequency of spontaneous closure during early infancy are higher than previously believed. This information is important for predicting the natural course of t-VSD and deciding on its proper management.
Collapse
Affiliation(s)
- S Hiraishi
- Department of Pediatrics and Cardiovascular Surgery, Kitasato University School of Medicine, Kanagawa, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Bai SL, Campbell SE, Moore JA, Morales MC, Gerdes AM. Influence of age, growth, and sex on cardiac myocyte size and number in rats. Anat Rec (Hoboken) 1990; 226:207-12. [PMID: 2301738 DOI: 10.1002/ar.1092260210] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The effects of altered neonatal nutrition on cardiac myocyte size and number was examined in 21-day-old and 3-month-old rats. Nutritional differences in growth rate were produced in newborns by adjusting litter size to four (fast-growing), eight (normally growing), or 16 (slow-growing) pups per litter. Isolated myocytes were prepared from animals in each group to evaluate changes in cell size and number. Heart weight (mg +/- S.D.), at 21 days of age, was 398 +/- 51 for "fast-growing" rats, 329 +/- 43 for "normally growing" rats, and 228 +/- 24 for "slow-growing" rats. Body weights showed a comparable decline with reduced nutrition. In adults, treatment-related differences in body and heart weight were present in males but not females. "Slow-growing" rats had 21% fewer myocytes than "fast-growing" rats at 21 days of age, a change that persisted in adults. Values for myocyte number from "normally growing" rats were intermediate between those of "fast and slow-growing" rats at both 21 days and 3 months of age. In each heart region of weanling rats, myocyte length and volume were smallest in 16 per litter rats. Cellular dimensions increased progressively with better nutrition.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- S L Bai
- Department of Anatomy, College of Medicine, University of South Florida, Tampa 33612
| | | | | | | | | |
Collapse
|
21
|
Engelmann GL, Boehm KD, Haskell JF, Khairallah PA, Ilan J. Insulin-like growth factors and neonatal cardiomyocyte development: ventricular gene expression and membrane receptor variations in normotensive and hypertensive rats. Mol Cell Endocrinol 1989; 63:1-14. [PMID: 2473931 DOI: 10.1016/0303-7207(89)90076-2] [Citation(s) in RCA: 91] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Defined factors regulating or influencing mammalian ventricular myocyte (cardiomyocyte) development are not known at this time. During early neonatal ventricular growth, cardiomyocytes begin a 'transition phase' of development toward cellular maturation (hypertrophy) that entails terminal proliferation and cellular binucleation. Insulin-like growth factor-I and -II (IGFs) are believed to play a major role in mammalian postnatal and fetal growth, possibly functioning in local environments which facilitate autocrine or paracrine tissue growth characteristics. Therefore, we examined the expression of the IGF genes and their corresponding membrane receptors in ventricles of normotensive and spontaneously hypertensive (SHR) rat pups during the first 7-14 days of age. We have determined: (1) by receptor crosslinking that neonatal ventricular membranes possess type 1 and type 2 IGF receptors; (2) by receptor binding analysis that type 1 IGF receptor concentration is elevated between days 1-7 in the SHR and shows an age-related decline in concentration and an increase in affinity in both strains; (3) by Northern blot analysis that neonatal rat ventricular tissue expresses primarily IGF-II RNA transcripts of 3.6, 2.3 and 1.7 kilobases (kb) in size, with low levels of IGF-I transcripts detected; (4) by slot-blot hybridization that SHR ventricles contain higher levels of IGF-II transcripts at 3 days of age; and (5) localized the IGF transcripts to ventricular myocytes by tissue in situ hybridization. These observations support a role for cardiomyocyte-produced IGFs that may be locally produced and act in an autocrine or paracrine fashion to modulate cardiomyocyte growth and maturation in the developing rat heart. Because both IGF receptor and IGF RNA transcript parameters differed in SHR hearts, genetically predisposed to hypertrophy, a potentially important biochemical alteration may be associated with the fetal/neonatal growth abnormalities of the developing heart in this rat strain.
Collapse
Affiliation(s)
- G L Engelmann
- Department of Heart and Hypertension, Research Institute of the Cleveland Clinic Foundation, OH 44106
| | | | | | | | | |
Collapse
|
22
|
Abstract
To separate the physiologic process of growth from the pathologic process of hypertrophy in rat hearts with myocardial infarction, we compared 32 young, actively-growing rats (initial age 7 weeks) with 45 mature, slowly-growing rats (initial age 18 weeks). Animals were sacrificed five weeks after induction of infarction. During this period, young animals had a 58% increase in body weight and mature animals an 8% increase (p less than 0.001). Cardiac hypertrophy was directly demonstrated by an increase in cell diameter, in both young and mature animals with more than 15% of the left ventricle infarcted (8.5 +/- 0.8 micron in controls vs. 10.2 +/- 1.4 micron in infarcted rats, p less than 0.01). Hypertrophy was further indicated by constant left ventricular weight despite myocardial loss due to infarction, and by constant viable tissue volume estimate ("remaining myocardial area"). Because of hypertrophy the total amount of remaining myocardial area was constant across subgroups with and without infarction (p greater than 0.2). Therefore, cardiac hypertrophy following infarction in rats is not dependent upon age.
Collapse
|
23
|
Kimball BP, Shurvell BL, Houle S, Fulop JC, Rakowski H, McLaughlin PR. Persistent ventricular adaptations in postoperative coarctation of the aorta. J Am Coll Cardiol 1986; 8:172-8. [PMID: 3711513 DOI: 10.1016/s0735-1097(86)80109-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
To evaluate ventricular performance and myocardial contractility after surgical correction of congenital coarctation of the aorta, we studied 25 patients (16 men and 9 women, mean age 26.1 years [range 19 to 34]), an average of 10.6 years (range 2 to 25) after repair. Radionuclide ventriculography at rest and exercise and digitized, quantitative two-dimensional echocardiography were performed. Data from derived, high resolution time-activity curves by radionuclide ventriculography, combined with noninvasive hemodynamic/ventricular volume data, were compared with values in an age- and sex-matched normal population. Despite essentially identical baseline and exercise hemodynamics, postoperative coarctation subjects demonstrated enhanced ventricular contraction, as determined by the peak ejection rate at rest (-3.79 versus -3.20 stroke volume/s, p less than 0.01) and exercise (-3.00 versus -2.90 stroke volume/s, p = NS), and overall ejection fraction at rest (56.4 versus 48.0%, p less than 0.01) and exercise (70.8 versus 59.3%, p less than 0.01). An intrinsic activation-contraction delay was observed, as illustrated by a prolonged time to peak ejection rate at rest (27.7 versus 21.5% of the RR interval, p less than 0.01) and exercise (28.4 versus 21.2% of the RR interval, p less than 0.01), and total systolic time at rest (50.2 versus 43.4% of the RR interval, p less than 0.01) and exercise (56.8 versus 50.4% of the RR interval, p less than 0.01). Although left ventricular meridinal wall stress was statistically indistinguishable (62 versus 74 mm Hg/mm2, p = NS), intrinsic myocardial contractility, as assessed by the peak systolic pressure/volume ratio, was increased in the postoperative coarctation group (1.88 versus 2.87 mm Hg/ml, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
|
24
|
Brodsky VY, Delone GV, Tsirekidze NN. Genome multiplication in cardiomyocytes of fast- and slow-growing mice. CELL DIFFERENTIATION 1985; 17:175-81. [PMID: 4053188 DOI: 10.1016/0045-6039(85)90485-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The number of myocytes and the percentage of cells with a high degree of ploidy increased in the heart ventricles of fast-growing mice compared with slow-growing ones. The mean incidence of octa- and hexadecaploid (by summary DNA content) myocytes was 7% in the slow-growing and 23% in the fast-growing, weaned mice. In these groups, the total myocyte number varied by 20%. There were 43% more myocyte genomes in the heart ventricles of the fast-growing mice than in those of the slow-growing mice. The same differences in cell number and ploidy persist in 90-day-old mice in spite of feeding ad libitum after weaning.
Collapse
|
25
|
Zuurveld JG, Wirtz P, Loermans HM, Veerkamp JH. Postnatal growth and differentiation in three hindlimb muscles of the rat. Characterization with biochemical and enzyme-histochemical methods. Cell Tissue Res 1985; 241:183-92. [PMID: 2992792 DOI: 10.1007/bf00214640] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The postnatal development, between 0 and 90 days, of three hindlimb muscles and diaphragm of the rat was investigated with respect to fiber types and diameter (histochemistry) and substrate oxidation rates and enzyme activities (biochemistry). The process of muscle fiber differentiation into mature patterns was evaluated by visual classification into 3 or 4 groups having different staining intensities for 3 enzyme-histochemical reactions, enabling 26 fiber types to be distinguished. These exhibited specific sizes and growth rates that varied among the muscles. One of the hindleg muscles (flexor digitorum brevis) remained much more immature than soleus and extensor digitorum longus. The histochemical and biochemical findings correlated well. The capacity for pyruvate and palmitate oxidation, and the activities of cytochrome c oxidase and citrate synthase, increased markedly between 9 and 37 days in soleus and extensor digitorum longus (except citrate synthase in the latter) but not in flexor digitorum brevis. Creatine kinase activity increased in all hindlimb muscles. Both the capacity and the activity of pyruvate oxidation (determined in homogenates and intact isolated muscles, respectively), were in accordance with the fiber type composition. In contrast to oxidation capacity, the activity of pyruvate oxidation decreased after birth until the mature stage, when a value of 18-42% of that of early postnatal muscles was recorded.
Collapse
|
26
|
Rakusan K, Hrdina PW, Turek Z, Lakatta EG, Spurgeon HA, Wolford GD. Cell size and capillary supply of the hypertensive rat heart: quantitative study. Basic Res Cardiol 1984; 79:389-95. [PMID: 6237640 DOI: 10.1007/bf01908138] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Cardiac mass, cell size and capillary supply were studied in the hearts of spontaneously hypertensive rats (SHR) and compared to genetically similar non-hypertensive Wistar-Kyoto (WKY) of three adult ages: 5, 15 and 23 months. The left ventricular weight of SHR was not significantly greater than that of WKY at 5 months, but was by 15 months and became even more so by 23 months. This increase could be attributed to hypertrophy of the individual cardiac muscle cells and therefore, the estimated total number of myocytes per left ventricle was essentially the same in all experimental groups. Various indices of the myocardial capillary supply were also investigated. Cardiac hypertrophy in older hypertensive rats was characterized by greater and more variable intercapillary spacing, which may have importance in myocardial oxygen supply.
Collapse
|
27
|
Abstract
This report deals with increased cardiac mass in the light of the following variables: normal ventricular growth (embryo, fetus, neonate and child), the response to work loads (hemodynamic stress) and hypoxia, the cell responses of hyperplasia (increase in cell number), hypertrophy (increase in cell size) and the type of cell (muscle or connective tissue), the age or maturity of the myocardium at the time the hemodynamic or hypoxic stress is imposed, and the biochemistry, ultrastructure and functional morphology (modeling) of the ventricles in response to volume or pressure overload. The desirable physiologic adaptations to work loads are characterized, and the transition from physiologic to pathologic states is examined, comparing and contrasting increased ventricular mass in patients and in trained athletes. Regression of increased ventricular mass is then discussed, first at the cell level (hypertrophy/hyperplasia; muscle cell/connective tissue cell), then at the organ level. The requirements for maintaining or establishing normal ventricular function after removal of overload are reviewed, together with such variables as the type and duration of preoperative hemodynamic stress, the right versus the left ventricle and the relative rates of contractile protein synthesis and degradation.
Collapse
|
28
|
Glatz JF, Veerkamp JH. Postnatal development of palmitate oxidation and mitochondrial enzyme activities in rat cardiac and skeletal muscle. BIOCHIMICA ET BIOPHYSICA ACTA 1982; 711:327-35. [PMID: 6284242 DOI: 10.1016/0005-2760(82)90042-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
1. The palmitate oxidation rate was measured in intact diaphragm and m. flexor digitorum brevis and in whole homogenates of heart, diaphragm and m. quadriceps of developing rats between late foetal life and maturity. Activities of the mitochondrial enzymes cytochrome c oxidase and citrate synthase were also determined. 2. Immediately after birth the palmitate oxidation rate increases markedly in both intact diaphragm and m. flexor digitorum brevis and falls gradually after day 1 to adult values which are about 35% of those at birth. 3. The oxidation capacities of diaphragm and m. quadriceps, but especially of heart, increase steadily during development, starting before birth and reaching adult values at 15-20 days postnatally. The activities of the mitochondrial enzymes show a similar developmental pattern. 4. In heart the increase of oxidative capacity is the result of an increase of both mitochondrial content and mitochondrial activity. The mitochondrial contents of diaphragm and m. quadriceps, on the other hand, decrease with age and the increase of their oxidative capacities is due to a large rise of the mitochondrial activity.
Collapse
|
29
|
Porta EA, Sablan HM, Joun NS, Chee G. Effects of the type of dietary fat at two levels of vitamin E in Wistar male rats during development and aging. IV. Biochemical and morphometric parameters of the heart. Mech Ageing Dev 1982; 18:159-99. [PMID: 6174833 DOI: 10.1016/0047-6374(82)90085-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
|
30
|
Marino TA, Biberstein D, Severdia JB. The ultrastructure of the atrioventricular junctional tissues in the newborn ferret heart. THE AMERICAN JOURNAL OF ANATOMY 1981; 161:383-92. [PMID: 7282572 DOI: 10.1002/aja.1001610404] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
In this study the structure of the atrioventricular (AV) node and bundle in the newborn ferret heart was examined by light and electron microscopy. At the light microscopic level the AV node could be subdivided into deep and superficial portions. Electron microscopy revealed that both superficial and deep AV nodal cells were characterized by a paucity of myofibrils, desmosomes, fasciae adherentes and gap junctions. Deep V nodal cells, however, had more surface specializations than did superficial AV nodal cells. In both subdivisions the constituent cells were ellipsoid with tapering end-processes. In contrast to the nodal cells, the newborn AV bundle cells were round to ovoid. The AV bundle cells were organized into large fascicles, and there was a high frequency of anastomosing intercommunication between fascicles. These bundle cells had few myofibrils and high incidence of apposed plasma membrane. The present morphological findings support the concept that there are significant postnatal morphological changes that occur in the region of the AV junction. These results are also consistent with findings in other species that AV nodal conduction time is similar in newborns and adults, while conduction through the AV bundle increases with age.
Collapse
|
31
|
Hatt PY, Rakusan K, Gastineau P, Laplace M, Cluzeaud F. Aorto-caval fistula in the rat. An experimental model of heart volume overloading. Basic Res Cardiol 1980; 75:105-8. [PMID: 6446282 DOI: 10.1007/bf02001401] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Abdominal aorto-caval fistula was experimentally induced in rats, and animals were sacrificed 5 days, 1 month, and 6 months later. Cardiac weight almost doubled the normal weight during the first month. Cell length increased to the same extent as the cell width, indicating harmonious growth. Increase in cell volume, as well as the amount of degenerative changes, were more pronounced in subendocardium than in midwall and subepicardium. Cytological features of active cellular growth was found not only in the early stages (5 days and 1 month) but also 6 months after the operation. This finding is consonant with proteosynthesis stimulation not only in the early period of constitution of hypertrophy but also in the later stages.
Collapse
|
32
|
Abstract
The causal relation between cardiac function and growth is analyzed in this review article. Three different levels of development are discussed: cytodifferentiation, embryogenesis and postnatal development. The earliest stage of cardiac morphogenesis, that is, the appearance of cell-specific proteins and of spontaneous contractions, appears to be independent of hemodynamic forces. Also, the first major morphologic transformation of the primitive heart, looping, is the intrinsic property of the heart itself. However, at any later stage of life, hemodynamic function in both health and disease is closely coupled to cardiac growth.
Collapse
|
33
|
Page E. Quantitative ultrastructural analysis in cardiac membrane physiology. THE AMERICAN JOURNAL OF PHYSIOLOGY 1978; 235:C147-58. [PMID: 364994 DOI: 10.1152/ajpcell.1978.235.5.c147] [Citation(s) in RCA: 171] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Quantitative measurements on electron micrographs of heart muscle can yield information useful for cellular physiologists and at present not obtainable in other ways. These methods are subject to preparative artifact, sampling problems, and problems inherent in the mathematical description of ultrastructure. Nevertheless they provide the best available data for membrane areas of the plasmalemma and its components, as well as for membrane areas of the sarcoplasmic reticulum and mitochondria. Morphometric methods can be used to study growth of membranes. Changes in the volumes of intracellular membrane-limited subcompartments can also be measured. Quantitative analysis of freeze-fractured membrane replicas can be carried out either by a statistical approach or by optical diffraction. In this way, physiological perturbations or developmental events leading to changes in membrane permeability can be studied for correlated changes in membrane structure.
Collapse
|